Electrical power package for subsurface detonation of explosives

ABSTRACT

A POWER PACKAGE FOR ACTUATING SUB-SURFACE DEVICES, SUCH AS DETONATING SUB-SURFACE EXPLOSIVES, WHICH REQUIRES NO EXTERNAL ELECTRICAL CONNECTIONS, AND WHICH CAN BE FREELY DROPPED INTO A BOREHOLE, OR ALTERNATIVELY LOWERED INTO THE BOREHOLE ON A SLICK LINE. THE SUB-SURFACE DEVICE HAS AN ELECTRICAL CONNECTION MEANS THEREON WHICH COOPERATES WITH AN ELECTRODE OF THE POWER PACKAGE SO AS TO COMPLETE THE CIRCUITRY THEREOF AND DETONATE OR ACTUATE A SUB-SURFACE DEVICE.

Feb. 20, 1973 R. R. VANN EIAL 3,71?,9

ELECTRICAL POWER PACKAGE FOR SUB-SURFACE DETONATION OF EXPLOSIVES Filed Jan. 25, 1971 A" f f 4 r 735 f j I II, l 5 158 f 5 2,46 ,45

If\'\'l:.\"1'(,)R. ROY R. VANN 8a CLYDE R. VANN MARCUS L. BATES THEIR AGENT United States Eatent 3,717,099 ELECTRICAL POWER PACKAGE FOR SUB- SURFACE DETONATION F EXPLOSIVES Roy R. Vann and Clyde R. Vann, Midland, Tex. (Box 40-A, Star Route West, 1112-B Hermosa Drive, both of Artesia, N. Mex. 88210) Filed Ian. 25, 1971, Ser. No. 109,382 Int. Cl. F42c 19/12; F42d /00; H01h 3/16 US. Cl. 102-702 R 3 Claims ABSTRACT OF THE DISCLOSURE A power package for actuating sub-surface devices, such as detonating sub-surface explosives, which requires no external electrical connections, and which can be freely dropped into a borehole, or alternatively lowered into the borehole on a slick line. The sub-surface device has an electrical connection means thereon which cooperates with an electrode of the power package so as to complete the circuitry thereof and detonate or actuate a sub-surface device.

BACKGROUND OF THE INVENTION Providing a source of current to a sub-surface device located thousands of feet beneath the surface of the earth is a complex endeavor because the borehole may be under several thousand p.s.i. and it may also be loaded with hydrocarbons or salt water, and accordingly, in using wire line devices wherein the current must be supplied through the supporting cable requires a substantial amount of above surface equipment, as well as an exceptionally well insulated conductor contained within the supporting wire.

It is therefore desirable to provide a power package for supplying a source of current to various sub-surface equipment associated with the borehole, wherein the equipment requires that a difference in potential be connected thereto in order that it may be activated. Throughout this disclosure, the present power package is explained in conjunction with a jet perforating gun; however, it should be understood that the usage of the power package of this invention can be extended into usage with other devices, such as, for example, setting a packer, commencing operation of recording devices, and detonating other known sub-surface explosive devices in addition to those referred to herein.

It is desirable that such a power package have the capability of being run into a borehole on a slick line. Alternatively, the power package may be freely dropped into the borehole, depending upon the design of the subsurface equipment and the circumstances of the particular operation.

For further background of sub-surface equipment which can be actuated by this invention, reference is made to my copending application Ser. No. 80,991, filed Oct. 15, 1970.

SUMMARY OF THE INVENTION This invention discloses a power package for use in detonating sub-surface explosives, or otherwise actuating sub-surface apparatus which requires the provision of an external electrical current of limited duration. The invention includes a housing within which there is disposed one or more storage batteries hermetically sealed therewithin, and having an electrode extending through the body thereof with the electrode being insulated in a particular manner so as to provide a difference in potential across one extremity of the electrode and the housing. The power package cooperates with a downhole sub assembly in a manner that when the electrode of the power package is brought into contact with an electrical connection of the sub assembly, current from the battery contained within the power package is brought into electrical contact with circuitry associated with the sub assembly.

A primary object of the present invention is the provision of a power package for providing a source of current to a sub assembly located downhole in a borehole.

Another object of this invention is the provision of a power package having storage batteries contained therein, and which can be freely dropped within a tubing string so that when the power package contacts a special sub assembly, a difference in potential is provided at the sub assembly so as to enable actuation of electrically actuated apparatus associated with the sub assembly.

A further object of this invention is the provision of improved means for detonating sub-surface explosive devices.

Still a further object of this invention is the provision of an improved power package which cooperates with a special sub assembly so as to enable downhole equipment to be electrically actuated in a new and improved manner.

The above objects are attained with apparatus made in accordance with the above abstract and summary of the present invention.

Various other objects and advantages of this invention will become readily apparent to those skilled in the art upon reading the following detailed description and by referring to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a part schematical, part diagrammatical representation of a cross-section of the earth, showing a borehole within which there is disposed apparatus made in accordance with the present invention;

FIG. 2 is an enlarged, fragmentary, longitudinal crosssectional representation of part of the apparatus illustrated in FIG. 1;

FIGS. 3-7, respectively, are cross-sectional views taken along lines 33, 4-4, 55, 6-6, and 7-7, respectively, of FIG. 2.

DETAILED DESCRIPTION OF THE EMBODIMENT "FIG. 1 shows a well head 10 extending from the surface 11 of the ground and communicating with a borehole 12, which usually is provided with a casing. Centrally disposed within the borehole is a production tubing 13, which cooperates with the casing to form two separate flow paths 14 and 15.

The well head may arbitrarily include the usual Christmas tree having various outflow valves and perhaps a lubricator as diagrammatically seen at numerals 16, 17, and 18.

The borehole extends through various strata of the earth as generally seen at 19. The strata at 19 is often perforated, as indicated by the numeral 20, so as to enable production to occur within annulus 14.

Packer 21 isolates annulus 14 from annulus 22. The packer is located above a perforated nipple 23, with the nipple being attached to a gun head sub assembly 24, made in accordance with the present invention. A large casing type jet perforating gun 25 is comprised of a cylinder 26 having a plurality of jet charges 27 disposed therein so that when the charges are properly detonated the strata adjacent to the casing is penetrated in a manner indicated by numeral 28. In some instances, as pointed out in my copending application Ser. No. 80,991, it is advantageous to use jet charges capable of deep penetration of the various strata indicated by the nu merals 29, 30, and 31.

A power package for actuating the sub-surface apparatus, such as the sub-surface explosive device seen at 25,

is seen suspended within the tubing string at 32, with the upper extremity of the apparatus being supported by a slick line at 33, although the slick line is not always required, as will be better appreciated later on in this disclosure.

Looking now to the details of FIG. 2, in conjunction with the remaining figures, the power package 32 is seen to have an upper marginal end portion 34, hereinafter referred to as sub 34, in the form of a fishing. neck, with the free end of the upper extremity being threaded so as to enable it to receive a rope socket or the like when it is deemed desirable to make attachments thereto. The package includes a cylindrical housing 35 having the illustrated internally threaded upper marginal end portion which threadedly engages the sub 34. O-ring seals are disposed within the circumferentially extending grooves 36 to preclude flow of fluid past the internally threaded area.

The lower marginal portion of the housing is provided with internal threads for receiving sub 37 therein. The housing, together with the opposed subs, form a chamber 38 which is illustrated as being a longitudinally dis posed cylindrical chamber. The lower face of sub 34 has the illustrated circumferentially extending groove formed therein which removably receives the enlarged end of a spring 39 therein. The sub 37 has a longitudinally disposed, axially aligned counterbore formed therein which receives an electrical connector 40 therethrough. The connector threadedly engages electrode 41 by the illustrated threaded connection. The annulus formed between the counterbore and the connector is tightly filled with a machined insulator 42. The lower sub is reduced at 43' to form a downward projection 43. Spaced apart circumferentially extending grooves 43" are formed on the projection and on the electrode so as to enable a rubber sleeve to be placed therebetween when deemed desirable Insulator 44 electrically separate the electrode from the projection. Threaded area 45 enables insulator 42 to be affixed to a marginal upper portion of the counterbore formed within sub 37.

A plurality of batteries 47 are series connected together and disposed between the electrical connectors formed at 46 and 47'. O-ring seal 48 is seated within the illustrated circumferentially extending groove and preclude flow of fluid past the threaded area of the lower sub and into the chamber 38.

A third sub 49 forms part of the gun head 24 and includes an upwardly extending insulator 51 which is coextensive for a limited longitudinal distance within tubing 52. A collar 24' has attached thereto a plurality of inwardly and downwardly turned spring steel members 53 which are mechanically and electrically attached to the collar at 53'. The steel members form scratchers and extend inwardly from the collar interior a sufficient amount to electrically contact the exterior surface of housing 35, but are spaced sufficiently far enough apart with respect to one another to enable the free end portion at 53 to clear the electrode.

Upwardly depending from the third sub is an electrical contact which is electrically insulated from the chamber 50 by means of insulation 54. Upper horizontal face 55 of the third sub can be electrically insulated from well fluids by pouring a thin film of epoxy thereon, if deemed desirable to do so. Insulation 56 preferably is an epoxy cement or potting compound which fills the enlarged portion of the illustrated axial counterbore and which rigidly aflixes the contact to the sub. The counterbore also receives therein the insulators 57 and 58, with insulator 58 being in the form of a washer which is disposed at the lower extremity thereof. The reduced passageway 59 is of a sufficient size to freely receive conductor 60 therethrough, with the conductor being connected to various sub-surface apparatus which preferably is located at 26, for example.

The face 62 of the electrical conductor is made of low resistance material, such as copper, which can also be coated with insulating material, so long as the point of electrode 41 will be able to penetrate the insulation material or coating, to thereby make direct electrical contact with the copper face when the two are brought together.

OPERATION In operation, the apparatus of the present invention is assembled by cementing electrical connector 40 within the tubular insulator 42. The insulator is next screwed into the lower sub 37, after which the insulator 44 is properly positioned within the illustrated counterbore, and the electrode 41 is then firmly tightened onto the threaded connector so as to elfectively seal the longitudinally extending axial passageway of the sub. O-ring seal 48 is next placed into the illustrated groove, and the sub is tightly made up to the lower marginal end portion of the housing. The batteries are next placed into the chamber after which the upper sub is tightened so as to preclude leakage across O-ring seal 36. Obviously, the marginal inside peripheral wall surfaces of the housing which receive each of the O-rings should be polished and made of a tolerance which will enable a hermetic seal to be effected.

Where deemed desirable, the lower portion of the power package can be dipped in a suitable electrical insulation, as for example, varnish, epoxy compound, or Glyptal. Of course, the lower extremity of the electrode at the point 41 must either be devoid of insulation or it must alternatively have an insulation coating thereon which will be penetrated when the sharp point thereof is brought into contact with face 62, so that metal to metal engagement results in the establishment of a current flow path.

Thea power package can be run into the borehole on the end of a slick line when deemed desirable, or alternatively, it can be freely dropped into the tubing string, thereby permitting the apparatus to free fall to the bottom f the well where point 41 contacts face 62 of the conductor. As the electrode abuts the face of the conductor, the scratoher springs come into electrical contact with the outside peripheral wall of the housing, thereby establishing a electrical circuit which can be traced from the batter es, through the electrical connection at 46, through conductor 40, to the electrode 41 and into the face 62 of conductor 61, where current will then flow through the insulaile'd wire 60 and on to the sub-surface electrically actuate device. Return current flow is traced through a ground circuit provided by the third sub 49, through th tubing and into collar 24', through the wire springs 53, into the housing 35, into sub 34, through spring 39, and back to the battery at 47', thus completing the circuit.

The present invention is particularly adapted for detonating sub-surface explosive devices such as disclosed in patent application Ser. No. 80,991, for the reason that the power package together with the firing head of the explosive device can be arranged in a manner to preclude the power package being forced back uphole, with a piston-like action and at dangerous velocities which may carry away part of the well head. Looking at FIG. 1, for example, the power package can be dropped into the we head where it will fall through the tubing, through the vent string 23, and on downhole to where the electrode of the package comes to rest within gun head subassernbly 24, thereby detonating the jet gun 25. Hence, the power package comes to rest in a quiescent area of the production tubing, and the blast from the explosion along with subsequent production will occur through annulus 22, through the perforated nipple 23, and back up through the tubing string, without exerting any upthrust upon the power package. The power package may be abandoned, or it may be retrieved later on by a fishing tool.

Where it is desired to use a slick line in conjunction with the power package, the diameter of the slick line is of a sufficiently small size to preclude upthrust of the line with a resultant force which is suflicient to either lift the power package or cause parting of the slick line. Generally a slick line will be used in a dry hole while the apparatus will be freely dropped where there is a column of liquid in the hole to decelerate the package.

The particular batteries used at 47 are identified as number 226 Everready transistor 9 volt batteries since these particular batteries can be series connected by th snap-like central fittings provided thereon by the manufacture. Other batteries can be substituted for these three 9 volt batteries if deemed desirable, and furthermore, the housing can be modified to accept additional batteries where an increased voltage is required.

The present invention also enables simplification of well completion in that the blankng plug which is sometimes used to isolate apparatus 24 can be eliminated. This is possible by the provision of an apertured sliding sleeve which is slidably placed within and adjacent to the perforated nipple 23 with the apertures being misaligned with respect to the perforations. When it is desired to complete the well, the power package is lowered on the slick line, the sleeve within the perforated nipple engaged with structure of the power package, and the perforations therein opened by aligning the apertures with the perforations, and thereafter the power package is further lowered where it comes into contact with the electrical conductor at 62 to thereby complete the well, all in a single trip, by merely using a slick line.

The actual difference in potential usually required at 60 is generally less than five volts, with sufiicient amperage to cause detonation of a blasting cap. Accordingly, as the power package is lowered into the borehole, should it contact salt water, the conductivity from point 41 to the exposed metal at 43 represents a current loss which will not preclude operation of the device. Where the lower extremity from 43 to the point 41 has been entirely coated with a suitable insulation material, there can be no inadvertent current flow because of the presence of well fluid. Where a rubber sleeve is dispos d between the spaced apart grooves 43", there can be a li ited amount of current flow, however the magnitude f the current fiow is far less than would be anticipated. For example, in saturated salt water, which is the worse condition possible, there will still be sufiicient current flow from electrode 41 into face 62 for actuating or detonating the sub-surface device.

I claim: 1

1. Apparatus for electrically detonating a subsu face explosive located downhole in a borehole, comprising:

a power package adapted to be run through a tubing string, a gun head adapted to be located at the lower terminal end of the tubing string, circuit means by which the gun head can detonate a sub-surface explosive when the power package is brought into contact therewith;

said power package including an elongated housing having a chamber formed therein, closure means at each end of the chamber, said chamber being adapted to contain a source of electrical power therein;

an electrode axially aligned with and depending from said housing, means insulating said electrode in fixed relationship with respect to the last said closure means and said housing; the depending end portion of said electrode terminating in a sharp point;

circuit means forming a current flow path from the source of power, to said housing, and from the source of power to said electrode, to thereby provide a difference in potential bet-ween the housing and the electrode;

said gun head including means forming an upwardly opening insulated chamber which is in communication with the interior of the tubing string within which the power package can be received;

a collar affixed to said gun head and adapted to be connected to the tubing string, a plurality of radially spaced apart spring members having a free end portion and a fixed end portion with the fixed end portion being afiixed to the inside wall of said collar, said spring members having the free end portion inwardly directed towards one another and spaced apart from one another an amount to freely receive said electrode therethrough, and to contact said housing when the power package is telescopingly received through said collar;

a conductor means which includes a fixed end and a free end portion, insulation means by which said conductor means is affixed to said gun head; said free end portion of said conductor having an enlargement which defines an upwardly disposed face which is axially aligned with said chamber; whereby:

said power package, when lowered into contact with said conductor means, establishes a current flow path from said electrode into said face, from said face to the sub-surface apparatus, from the sub-surface apparatus to the spring members and into said housing to thereby enable the source of power to provide the subsurface apparatus with a flow of current.

2. The apparatus of claim 1, wherein said electrode is provided with an insulation means which must be penetrated by said conductor means in order for current to flow from said power package.

3. The apparatus of claim 1 wherein said closure means at each extremity of said housing includes an upper sub and a lower sub; said electrode being affixed to said lower sub; and means afiixed to said upper sub for enabling said power package to be supported by a slick line.

References Cited UNITED STATES PATENTS 2,566,682 9/1951 Sweetman 102-20 X 2,620,029 12/1952 Turechek etal 102-20X 2,931,874 4/1960 Leaman 102- 70.2 R 3,088,006 4/1963 K'abik et 'al 102-702 A 3,457,431 7/1969 Zingg et a1. 102 70.2 R

BENJAMIN A. BORCHELT, Primary Examiner T. H. WEBB, Assistant Examiner US. Cl. X.R. 20061.53 

